Process of treating mixed lead-zinc sulphide ores



. Patented Feb. 9. .1926. a t I I v UNITED STATES PATENT OFFICE.

NIELS C. CHRISTENSEN, OF SALT LAKE CITY, UTAH.

PROCESS OF TREATING MIXED LEAD-ZINC SULPHIDE ORE S.

No Drawing.

new and useful Improvements in' Processes of Treating Mixed Lead-Zinc Sulphide Ores, of which the following is a specifica tion. 1 I

This process relates to the treatment of lead and zinc sulphide ores for the recovery of lead and zinc therefrom, and particularly the recovery of-these in separate products. In part this process is an improvement of or addition to the process disclosed in my patent applications Serial Nos. 327,400, 329,333, 372,691. The process is applicable to the treatment of zinc ores alone but is especially applicable to the treatment of the mixed or socalled complex sulphide ores of zinc and lead.

I have found that if such ores are treated with an acid brine that all the lead and part of the zinc may be dissolved in the brine the lead and zinc going into solution as chloride and the sulphur being driven off as H S. as indicated below:

solution with sulphates.

The brine may be made with any of the common chlorides such as NaCl, CaCl MgCl or a mixture of these, though in most cases NaCl or a mixture of N001 and OaCl will be used. Either HCl or H SO may be used to add to the brine though the former is preferable as the latter contaminates the Either a hot or cold brine may be used in the process. If it is desired to dissolve as little zinc as possible a cold solution with a minimum of acid may be used. If it is,desired to shorten the time of treatment as ueh as possible, and at the same time dissolve as little zinc as possible, a hot solution may be used with a minimum of acid. These cases would apply particularly to a 'zinc concentrate carry ing lead which it is desired to remove. If it is desired to dissolve not only the lead but also to dissolve out all the zinc possible, as might be the case in the treatment of a Pb-Fe concentrate in which the yrite residue contains gold and silver and would be shipped to a smelterfor treatment, the hot brine with an excess of acid would be used.

The process is particularly directed to the Application filed December 31, 1923. Serial No. 683,823.

precipitation of the lead and zinc from th brinein separate products.

My method consists in using the H S as a precipitant in combination with calcium hydroxide or lime. in such a manner as to secure'the lead and zinc as separate precipi tated sulphide products, in the manner as described below. I have found. that the lead and zinc may be completely separated from the brine solution by the addition of finely ground Ca(OH) and thus first precipitating them as hydroxides and thereafter adding H S to the solution, and converting the hydroxides to sulphides as indicated below:

ZnS will completely precipitate the Pb from the solution as indicated below:

ated from the solution by the addition of Gas or CA (SH) made by absorbing the H s, made in the treatment of the ore with the acid brine, with Ca(OI-I) or lime as indicated below:

The use of the Ca(HS) as the precipitant is much preferred as it is soluble and may be used in solution but has the disadvantage of requiring the reabsorption of the excess molecule of H S if it is desired to use this over again in the process. The Gas being in JSOlld. form precipitates the sulphides around the particles of Gas and prevents complete using up of the Gas and thus contaminates the products with the Gas. My

Zinc may be completely precipitatedthe addition of more Ca (HS) To get the exact amount of Ca(SH) to precipitate the Pb alone is diflicult the products would in most cases be contaminated, either the lead with zinc or the 'zinc with lead according lead sulphide precipitate. -Then enough Ca(HS) to precipitate the residual lead and a small amount of zinc is added. Then -enough Ca(HS) to precipitate the zinc is added giving a lead free zinc sulphide precipitateJ The small mixed "zinc lead sulphide precipitate is added to the original solution before any Ca(HS) is added. The

zinc sulphide in this precipitates the'lead as a sulphide and the zinc goes into solutionas zinc chloride. In this way the zinc and lead are secured as two separate clean sulphide precipitates.

This process is applicable to the treatment of lead, zinc ores or concentrates in which the primary object is the recovery of the lead and the recovery of incidentally dissolved zinc is secondary and is also applicable to the treatment of ores and concentrate in which the object is'not only to recover the lead but also to recover as much of the zinc as possiblefrom the ore or prodnot.- The method of treating the ore or product will depend upon the; object of the treatment. If it is desired to recover the lead and dissolve as little zinc as possible, the ore may be treated with, afcold acid brine. If the object is to recover the lead and dissolve out all the zinc possible the ore may be treated with a hot acid brine, and part of the lead may be recovered as a chloride. In any case, however, the lead and zinc recovered will be recovered substantially in the manner described. If itis desired to recover all the lead as a chloride from a hot solution, the lead precipitated as a sulphide may be redissolved in the hot acid. brine in the treatment of more ore. In this case it is not necessary tobe soexact in the method of precipitating the lead as any small amount of zinc sulphide mixed with the lead wouldbe dissolved in the acid brine and not being precipitated by cooling would separate from the lead.

Having described my process, what I claim and desire to patent is;

the zinc sulphide out and driving ofl the sulphur combined with said metals as H 8 and treating said H S ;1. The rocess of treating lead-zinc ores.

brine and thereby dissolving the lead and some of the zinc as chlorides in said brine with lime to form calcium sulph-hydrate and i using said calcium sulph-hydrate to ,precipitate from said brine solution as sulp'hi first the lead, and thereafter the zinc, substantially as described.

2. The process of treating lead-z inc-ores finely ground ores with an acid concentrated brine and thereby dissolving .the lead and some of the zinc as chlorides in said brine and driving oil the sulphur combined with said metals as H 8 and treating said H' S with lime to form calcium sulph-hydrate and using said calcium sulph-hydrate to precipitate from'said-brine solution first lead as a sulphide, thereafter a mixture of lead and zinc sulphides, and then zinc as a sulphide, substantially as described.

3. The "process of treati and the like which consists in mixing said finely. ground ores with an acid concentrated brine and thereby dissolving the lead and some of the zinc as chlorides in said brine and driving off the sulphur combined with said metals as H S', andtreating said H 8 with-"lime to form calcium sulph-hydrate,

and the like which consists in mixing said I I ng lead-zinc ores and using said calcium sulp'h-hydrate to precipitate from said brine solution first lead as a sulphide, thereafter amixture of lead and zinc sulphides, .and then zinc as a sulphide, substantially as described, and

adding-said mixed precipitates of lead and K zinc sulphides to other unprecipitated brine solution and thereby precipitating lead as a sulphide from said solution and dissolving of said mixed precipitates.' I

4- The process of treating lead-zgn'c ores and the like which consists in mixing said finely ground oreswith an acid concentrated brine and hereby dissolving the lead and some of the zinc as chlorides in said brine and driving ofi' the sulphur combined with said metals asH S, and treating said H,S with lime to form calcium sulphshydrate and using said-calcium sulph-hydrate to precipitate from said brine solution zinc sulphide and using said zinc sulphide to precipitate lead as a sulphide from other brine solution.

- NIELS o. CHRISTENSEN. 

